Powder magnetic core, and coil component

Abstract

A method for manufacturing a powder magnetic core using a soft magnetic material powder, wherein the method has: a first step of mixing the soft magnetic material powder with a binder, a second step of subjecting a mixture obtained through the first step to pressure forming, and a third step of subjecting a formed body obtained through the second step to heat treatment. The soft magnetic material powder is an Fe—Cr—Al based alloy powder comprising Fe, Cr and Al. An oxide layer is formed on a surface of the soft magnetic material powder by the heat treatment. The oxide layer has a higher ratio by mass of Al to the sum of Fe, Cr and Al than an alloy phase inside the powder.

What is claimed is: 
     
       1. A powder magnetic core, comprising a soft magnetic material powder,
 wherein the soft magnetic material powder is an Fe—Cr—Al based alloy powder consisting essentially of Fe, Cr and Al, 
 a space factor of the soft magnetic material powder is 80 to 90%, 
 particles of the soft magnetic material powder are bonded to each other by an oxide layer having a higher ratio by mass of Al to the sum of Fe, Cr and Al than an alloy phase inside the powder, 
 an average of respective maximum particle diameters of the particles of the soft magnetic material powder in an image obtained by observing a cross section of the powder magnetic core is 15 μm or less, and 
 in an image obtained by observing a cross section of the powder magnetic core, the proportion of the number of particles having a maximum diameter of more than 40 μm is less than 1.0%. 
 
     
     
       2. The powder magnetic core according to  claim 1 , wherein the Cr content in the soft magnetic material powder is from 2.5 to 7.0% by mass, and the Al content therein is from 3.0 to 7.0% by mass. 
     
     
       3. The powder magnetic core according to  claim 1 , wherein the average of the respective maximum particle diameters of the particles of the soft magnetic material powder in an image obtained by observing a cross section of the powder magnetic core is 8 μm or less. 
     
     
       4. A coil component, comprising a powder magnetic core according to  claim 1 , and a coil wound around the powder magnetic core. 
     
     
       5. The powder magnetic core according to  claim 1 , wherein the oxide layer has a part in which Fe is larger in proportion than Al.